3.1. IGP-Prefix Segment (Prefix-SID)

An IGP-Prefix segment is an IGP segment attached to an IGP prefix. An IGP-Prefix segment is global (unless explicitly advertised otherwise) within the SR domain. The context for an IGP-Prefix segment includes the prefix, topology, and algorithm. Multiple SIDs MAY be allocated to the same prefix so long as the tuple <prefix, topology, algorithm> is unique.

Multiple instances and topologies are defined in IS-IS and OSPF in: [RFC5120], [RFC8202], [RFC6549], and [RFC4915].